Wafer level pre-packaged flip chip

ABSTRACT

A pre-packaged flip chip package that includes one or more dice on a semiconductor wafer is disclosed. In the various embodiments, an adhesive layer may be applied to a first side of a finished wafer, having connector pads formed thereon. The adhesive layer may include openings through which the connector pads may be accessed. Conductive elements may be positioned within the adhesive, and configured to electrically couple to the conductive elements.

RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.10/722,838, filed Nov. 26, 2003, which is a Divisional of U.S.application Ser. No. 09/505,018, filed Feb. 16, 2000, now issued as U.S.Pat. No. 6,710,454, which are incorporated herein by reference.

TECHNICAL FIELD

This invention relates generally to packaging of semiconductor devicesand, more specifically, to an improved flip chip package and method ofpre-packaging a flip chip.

BACKGROUND OF THE INVENTION

As demand for smaller, more powerful electronic devices grows,semiconductor manufacturers are constantly attempting to reduce the sizeand cost of not only semiconductor devices themselves but alsosemiconductor packaging. Smaller packages equate with highersemiconductor mounting densities and higher mounting densities allow formore compact and yet more capable devices.

With conventional packaging methods, a semiconductor die or “chip” issingulated from the silicon wafer and is encapsulated in a ceramic orplastic package having a number of electrical leads extending therefrom.The leads permit electrical connection between external components andthe circuits on the die. Although these packages have proven reliable,they are generally many times larger than the actual die. In addition,the configuration of these packages typically yields only a limitednumber of leads. For these reasons, conventional packaging techniquesare not particularly adaptable to high density packaging.

Accordingly, more efficient chip packages have been developed. One suchpackage is the “pin grid array” or PGA which utilizes a series of pinconductors extending from the face of the package. While PGAs provideincreased electrical interconnection density, the pins forming the PGAare fragile and easily bent. In addition, the PGA is relativelyexpensive to produce and of limited value when the package is to bepermanently mounted.

Similar to the PGA are various flip chip packages including the “ballgrid array” or BGA. Instead of pins, the BGA has an array of solderbumps or balls attached to the active face of the package in a processcalled “bumping.” The array of solder bumps is adapted to mate withdiscreet contacts on a receiving component. The package may besubsequently heated to partially liquefy or “reflow” the bumps, thusforming electrical connections at the discreet locations. Thistechnology is frequently referred to as “flip chip” because the solderballs are typically secured to the semiconductor package wherein thepackage is then “flipped” to secure it to the receiving component. Thepresent invention is directed primarily to flip chip packagingtechnology and the remainder of this discussion will focus on the same.

While flip chip processes have proven effective, problems remain. Forinstance, conventional flip chip technology requires an underfill layerbetween the semiconductor package and the receiving substrate. Theunderfill material reduces stress on the solder bumps caused by thermalmismatch between the semiconductor package and substrate. The underfilllayer further provides insulation between the device and substrate andprevents creep flow at the solder interface. Without the underfilllayer, repeated thermal cycling constantly stresses the solderinterconnections, potentially leading to failure.

Unfortunately, the underfill process is time consuming and expensive.For example, the equipment used to dispense the underfill must preciselymaintain the viscosity of the material, dispensing it at a particularflow rate and within a predetermined temperature range. Further, theunderfill process cannot be applied until the package is secured to itsreceiving substrate. Accordingly, the chip package and substrate designmust permit the dispensing equipment direct access to thepackage/substrate interface. And still further, since the underfillmaterial is distributed via capillary action, the time required tocomplete the underfill operation can be significant.

One method which avoids the use of underfill material involves the useof a resilient retaining member which supports a series of solderpreforms therein. The retaining member is sandwiched between conductiveelements such that the preforms effect electrical connectiontherebetween. Like underfill, however, the retaining member/solderpreform is only utilized during actual surface mounting of individualchips.

While underfill processes as well as retaining member/preforms are morethan adequate in many applications, current trends in IC fabricationfavor completing more and more process steps—many of which would notnormally occur until after die singulation—at the wafer level. Waferlevel processing is advantageous over conventional methods as it allowsmultiple ICs (equal to the number of die on the wafer face) to beprocessed simultaneously rather than serially as typically requiredafter die singulation. Accordingly, the time required to produce a givenIC device can be dramatically reduced.

While some processes lend themselves to wafer level processing, knownpackaging methods such as underfill and retaining member/preform methodsunfortunately do not. Thus, what is needed is a flip chip package thatcan be assembled at wafer level. What is further needed is a packagethat avoids the problems with underfill materials including troublesomedispensing and assembly cycle times. The present invention is directedto a package and method that addresses these issues.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a pre-packaged flip chip in accordancewith one embodiment, the chip shown attached to a substrate;

FIG. 2 is an exploded perspective view of the flip chip of FIG. 1;

FIG. 3 is a partial cut-away perspective view of an active side of apre-packaged flip chip in accordance with one embodiment (some sectionlines removed for clarity);

FIG. 4 is section view taken along line 4-4 of FIG. 3 illustrating oneembodiment (some section lines removed for clarity);

FIG. 5 is another section view taken along line 4-4 of FIG. 3illustrating another embodiment (some section lines removed forclarity);

FIG. 6 is another section view taken along line 4-4 of FIG. 3illustrating yet another embodiment (some section lines removed forclarity);

FIG. 7 is another section view taken along line 4-4 of FIG. 3illustrating still yet another embodiment (some section lines removedfor clarity);

FIGS. 8A-8I illustrate wafers at various processing stages according toone embodiment;

FIG. 9 is a partial cut-away perspective view of a pre-packaged flipchip in accordance with another embodiment (some section lines removedfor clarity);

FIG. 10 is a perspective view of a substrate for receiving thepre-packaged flip chip of FIG. 9;

FIG. 11 is a section view taken along line 10-10 of FIG. 9 illustratingone embodiment of the flip chip of FIG. 9 (some section lines removedfor clarity);

FIG. 12 is another section view taken along line 10-10 of FIG. 9illustrating another embodiment of the flip chip of FIG. 9 (some sectionlines removed for clarity);

FIGS. 13A-13K illustrate wafers at various processing stages accordingto another embodiment (some section lines removed for clarity); and

FIG. 14 illustrates an electronic system incorporating the pre-packagedflip chip in accordance with one embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings which form a part hereof,and in which is shown by way of illustration specific embodiments inwhich the inventions may be practiced. These embodiments are describedin sufficient detail to enable those skilled in the art to practice theinvention, and it is to be understood that other embodiments may beutilized and that process, electrical or mechanical changes may be madewithout departing from the scope of the present invention.

The terms wafer and substrate used in the following description includeany base semiconductor structure. Both are to be understood as includingsilicon-on-sapphire (SOS) technology, silicon-on-insulator (SOI)technology, thin film transistor (TFT) technology, doped and undopedsemiconductors, epitaxial layers of a silicon supported by a basesemiconductor structure, as well as other semiconductor structures wellknown to one skilled in the art. Furthermore, when reference is made toa wafer or substrate in the following description, previous processsteps may have been utilized to form regions/junctions in the basesemiconductor structure, and terms wafer or substrate include theunderlying layers containing such regions/junctions. The followingdetailed description is, therefore, not to be taken in a limiting sense,and the scope of the present invention is defined only by the appendedclaims and their equivalents.

Broadly speaking, the instant invention is directed to a “pre-packaged”flip chip integrated circuit (IC) device and method for producing thesame. Unlike conventional flip chip packages, the pre-packaged ICdescribed herein eliminates the need for underfill operations by forminga flip chip adhesive layer on the package prior to surface mounting. Tomaximize throughput, the adhesive layer is, in one embodiment, appliedat the wafer level. In this way, multiple dice (as many as the waferprovides) can be processed substantially simultaneously. Further, bypackaging the die at wafer level, the bare die is handled less oftenthan with conventional packaging operations, thus reducing theopportunity for damage.

Once the adhesive layer is applied, it is processed to produce one ormore holes or openings therethrough. In one embodiment, the openings areproduced by exposing and patterning a selected photoresist layer andthen chemically etching exposed portions of the adhesive layer toproduce the openings. However, other methods of creating the openingsare also contemplated.

The function of the openings is to provide access to connection pads onthe face of the IC device. An electrically conductive material is thendeposited into the openings in accordance with various methods asfurther discussed below. The pre-packaged flip chip is then ready forsurface mounting to a receiving component which, for simplicity, willhereinafter be referred to as a support. Examples of a support wouldinclude a die attach area of a printed circuit board (PCB) or otherdevice. The electrically conductive material is then re-flowed tointerconnect the circuits on the IC to conductors on the support.

By prepackaging the flip chip, messy, expensive, and time-consumingunderfill operations are avoided. In addition, by utilizing variousembodiments of the invention, the die may be packaged at wafer level,allowing greater manufacturing efficiencies including simultaneouspackaging of multiple dice. Furthermore, as described below, theinvention lends itself to multi-chip configurations, permitting packageshaving even greater mounting densities.

With this brief introduction, specific embodiments of the instantinvention will now be described. Although the description focuses onparticular embodiments, the reader is reminded that such embodiments areexemplary only and are therefore intended merely to teach one of skillin the art how to make and use the invention. Other embodiments arecertainly possible without departing from the scope of the invention.

FIGS. 1-3 show an electronic apparatus such as an IC package 100according to one embodiment of the invention. The terms “IC package” and“pre-packaged flip chip” are used throughout the specification to referto an IC device with its protective package and lead system that allowssurface mounting of the device to other electronic components such as areceiving support 102. In the context of chip scale devices (CSD), theIC device will hereinafter be described as a semiconductor device suchas a chip or die 104 having a first or active side 105 (see FIG. 3) anda second or back side 103. The active side 105 has an array ofelectrical connection points or “pads” 107 (see FIG. 3) which allowelectrical coupling to the electronic circuits 101 on the die 104. Thepads are coupled directly to the circuits or, alternatively, coupled toredistribution traces formed in the die 104 which themselves thenconnect to the circuits. The pads 107 operatively couple to an array ofmating conductors 109 on the support 102 (see FIG. 2) via conductiveelements 112 (see FIG. 3) as further discussed below.

FIG. 1 shows a flip chip adhesive layer 106 between the die 104 and thesupport 102. The adhesive layer insulates the conductive elements andprevents damage caused by repeated thermal cycling. For clarity, theadhesive layer 106 is partially removed in FIG. 3 to illustrate the pads107 on the die surface 105. The adhesive layer 106 bonds or otherwiseadheres to the die surface 105 to form the package 100.

One exemplary embodiment of the pre-packaged flip chip 100 is shown inFIG. 3. Here the die 104 is shown with the adhesive layer 106 attachedto form the package 100. To provide electrical interconnection to thepads 107 on the die, the adhesive layer 106 includes an array of holesor openings 108 which are substantially aligned with the pads 107 (notethat while the holes 108 are shown as rectangular, other shapes areequally within the scope of the invention). That is, when the adhesivelayer 106 is attached, the pads 107 are accessible through the openings108. The adhesive layer further defines a support mating surface 110which is adapted to adhere to the support 102 (see FIG. 2) as furtherdescribed below.

The adhesive layer 106 is, in one embodiment, an elastomer applied influid form (i.e., applied “wet”) where the fluid is subsequentlyhardened or cured, or alternatively, in tape-like or film form (i.e.,applied “dry”). In one embodiment, the adhesive layer comprises athermoplastic material that repeatedly becomes sticky under applicationof heat. In this case, the transition temperature of the thermoplasticmaterial is selected to ensure the material does not soften duringsolder reflow or other subsequent processing. In another embodiment, theadhesive layer is a thermoset material that permanently sets afterinitial curing. Alternatively, the thermoset material is a “B-stageable”material (i.e., having an intermediate stage in which the materialremains wholly or partially plastic and fusible so that it softens whenheated). In still yet another embodiment, the adhesive layer is apressure-sensitive film that adheres upon contact or under slightapplication of pressure.

The material used to form the adhesive layer 106 is selected toadequately protect the flip chip package 100 and the support 102 as thetwo components experience differential expansion during thermal cycling.In one embodiment, the layer is selected to provide a high modulus,effectively fastening the package 100 to the support 102 andsignificantly prohibiting relative expansion. In another embodiment, thelayer 106 is selected to provide a low modulus to allow the package 102to expand at a different rate than the support without overstressingeither the support 102 or the package 100.

To form the openings 108, various methods are used. For example, wherethe adhesive layer 106 comprises a film, the openings 108 are formedtherein by photo-chemical etching, laser cutting, die cutting, or othertechniques. One advantage to the film-type adhesive layer 106 is thatthe openings 108 may be formed, if desired, prior to assembly with thedie 104. By then precisely locating the adhesive layer 106 inregistration with the die 104, the pre-cut openings 108 are properlyaligned with the pads 107 on the die surface 105.

Alternatively, the openings 108 are formed in the adhesive layer 106after assembly to the die 104. This method lends itself to use witheither the film-type adhesive or the wet adhesive. With post-formationof the openings 108, the material used to form the adhesive layer 106 isselected so that the openings 108 can be formed using standardphotolithographic techniques.

Still referring to FIG. 3, each opening 108 has a conductive materialtherein which allows electrical connection through the adhesive layer106 to the pads 107 on the die surface 105. For simplicity, theconductive material is hereinafter referred to as solder element 112.However, those skilled in the art will realize that a variety ofconductive materials (e.g., lead-based and lead-free solders, conductivepolymers, conductive pastes, etc.) is usable without departing from thescope of the invention.

The solder elements 112, as described below, take various formsincluding cylindrical or column-shaped structures 112′ (see FIGS. 4-6)and sphere-shaped or ball-like structures 112″ (see FIG. 7). FIG. 4shows one embodiment of the solder element 112 wherein the element formsa solder column 112′ that is slightly recessed from the mating surface110. In this particular embodiment, the adhesive layer 106 includes achamfer 114 in the vicinity of the opening 108. The chamfer 114 andrecessed column 112′ are particularly advantageous for surface mountingmethods which utilize solder paste or flux on the receiving support 102(see FIG. 2). When the package 100 is surface mounted, any excesspaste/flux is accommodated by the void defined by the chamfer 114 andrecessed column 112′ rather than spreading across the surface 110 whereit can interfere with adhesion of the surface 110 to the support 102(see FIG. 2).

FIG. 4 further illustrates an optional protective coating 116 applied tothe back side 103 of the die 104. The coating 116 may be an epoxy orother similar material that hardens to protect the back side 103 whichwould otherwise be exposed after surface mounting as shown in FIG. 1.Additionally, the coating 116 may a single- or multi-layer material,e.g., an adhesive or adhesive-coated film, that is mounted or laminatedto the back side 103 of the die 104.

Other embodiments are also possible. For example, in FIG. 5, theconductive material once again forms a solder column 112′. However, inthis particular embodiment, the column 112′ has a generallyconvex-shaped head 118 that extends beyond or protrudes from the surface110. The solder column 112′ is heated sufficiently to become gel-likeduring surface mounting. When the package is brought into registrationwith the support 102 (see FIG. 2), the heads 118 wet the supportconductors 109 (see FIG. 2) while the surface 110 bonds to the support102 (see FIG. 2).

In still another embodiment such as that shown in FIG. 6, the soldercolumns 112′ are substantially flush with the surface 110. Thisparticular configuration is advantageous when utilizing a pressuresensitive adhesive layer 106 (i.e., an adhesive layer 106 that comprisesa flexible tape which adheres to the support under application ofpressure). Because, the solder columns 112′ are flush to the surface110, the adhesive layer 106 makes consistent, uniform contact with thesupport 102 (see FIG. 2). Once secured to the support 102, the packageis heated to reflow the columns 112′ and form the required electricalinterconnection.

The solder columns 112′ are advantageous as the column height can beadjusted to correspond to the desired adhesive layer 106 thickness.Further, the columns are able to deflect and twist to accommodaterelative motion between the die 104 and the support 102.

While the above-described embodiments utilize solder columns 112′, stillyet another embodiment utilizes solder balls 112″ as generally shown inFIG. 7. Like the embodiments described in FIGS. 4-6, the solder balls112″ can be recessed within the surface 110, protrude therefrom, or berelatively flush thereto. The solder balls 112″ are advantageous in thatthey are cost-efficient to produce and capable of being handled by mostsemiconductor processing machines. While not shown herein, the soldercolumns 112′ are, in one embodiment, formed by stacked solder balls112″.

Having described various exemplary embodiments of the pre-packaged flipchip 100, a method for producing the package will now be described inaccordance with one exemplary embodiment. In describing the method, onlythose processes necessary for one of ordinary skill in the art tounderstand the invention are described in detail. Other fabricationprocesses that are well known or are unnecessary for a completeunderstanding of the invention are excluded.

As mentioned above, various embodiments of the invention are perceivedto be particularly advantageous for pre-packaging dice at wafer level.Generally speaking, the method, according to one embodiment, comprisesapplying an adhesive layer to an entire side of a semiconductor wafer(see generally FIG. 8C) wherein the wafer comprises numerous dicethereon. As described above, the adhesive layer either includes or ismodifiable to include openings having conductive elements therein. Theadhesive layer adheres to each die on the wafer such that a conductiveelement is aligned and in contact with each pad on each die. The die isthen singulated from the wafer to produce a pre-package flip chip 100 asshown in FIG. 3 and discussed above.

With this general introduction, an exemplary method of making thepre-packaged flip chip in accordance is now described with reference toFIGS. 8A-8I. FIG. 8A shows a finished wafer 800 (i.e., a wafer that hassubstantially completed all fabrication processes) having a first oractive side or face 802 and a second or back side 804. Located on thewafer 800 is an array of dice 806. Each die 806 has an array ofconductive pads 808 as shown in FIG. 8B. The pads 808 permit electricalconnection to circuits on each die 806.

FIG. 8C illustrates an adhesive layer 810 placed over the active side802 of the wafer 800. In one embodiment, the adhesive layer 810comprises an adhesive film 810′ that bonds to the wafer 800. In anotherembodiment, the adhesive layer 810 comprises a fluid 810″ applied wetvia a dispensing apparatus 812 and evenly distributed over the firstside 802. The fluid 810″, in one embodiment, forms a layer that ishardenable via curing. By controlling the viscosity and volume of theadhesive liquid 810″ dispensed, the thickness of the adhesive layer 810is controlled. In one embodiment, the wafer 800 is spun to more evenlydistribute the liquid adhesive 810″. The wafer 800 emerges with auniform adhesive layer 810 covering the entire active side 802.

To protect the back side 804 of the wafer 800, the latter is, in oneembodiment, flipped and a protective coating 814 applied to the backside 804. In one embodiment, the protective coating 814 comprises a film814′ that bonds to the wafer 800. In another embodiment, the protectivecoating 814 comprises a fluid 814″ applied wet via another dispensingapparatus 816 and evenly distributed over the back side 804 (while theapparatus 816 is shown diagrammatically beneath the wafer 800, it wouldactually be oriented above the wafer during dispensing).

Once the adhesive layer 810 is applied, it is—in one embodiment—cured tosecurely bond it to the wafer 800. Curing may occur via the applicationof energy such as heat, light, or radiation (as shown by an energysource 818 in FIG. 8D).

Once cured, the adhesive layer 810 is locally removed, asdiagrammatically represented in FIG. 8E, from the area of each pad 808(see FIG. 8B). In other words, openings 820 are created in the adhesivelayer 810, the openings 820 providing access to the pads 808 on each die806 as generally shown in FIG. 8F. In one embodiment, the openings 820are formed by providing a photo-sensitive adhesive layer 810. By maskingthe appropriate areas of the adhesive layer 810 and exposing the latterto an energy source 819, such as a high intensity ultra-violet lightsource, as shown in FIG. 8E, the adhesive layer 810 is chemicallyaltered in the area of the openings 820. The alteration permits theareas to be selectively etched and removed to form the openings 820.Other methods of forming the openings 820 are also possible.

To accurately locate the openings, one or more datums (not shown) areprecisely located on the wafer surface. The adhesive layer is chemicallyor manually removed (in the vicinity of these datums) to expose thedatums. The masking apparatus then uses these datums to ensure accuratealignment of the openings 820 with the pads 808. Other methods ofaligning the openings 820 are also possible within the scope of theinvention.

Once the openings 820 are formed, a solder element 822 is insertedtherein. In one embodiment, the solder element comprises a solder ball822′ as shown in FIG. 8G. A solder ball 822′ is placed into each opening820 with the use of an apparatus 824 such as a pick-and-place machine(hereinafter PNP). The PNP picks up the solder ball 822′ and preciselyplaces it into each opening 820. To form a solder column, multiple balls822′ may be stacked in each opening 820 or, alternatively, the PNP isused to place a column of conductive material. The apparatus 824 is, inanother embodiment, a machine similar to the PNP but able to forcefullyeject the solder ball 822′ into each opening 820. The latter apparatusis advantageous when the solder ball 822′ is slightly larger than theopening 820 diameter.

In still yet another embodiment, a paste or gel-like conductive material822″ is placed into each opening 820 to form solder columns such ascolumns 112 in FIGS. 4-6. The material 822″ is dispensed directly intothe openings 820 with a dispensing apparatus 826 or, alternatively,applied using stencil/screen techniques (not shown).

Still other embodiments are possible for securing the adhesive layer andforming the conductive element. For instance, in the case of a wetadhesive layer, the material is a combination of underfill, conductivefillers, and flux components that are spin-coated or stenciled over thewafer. The conductive fillers migrate through the liquid adhesive andaccumulate at the connection pads via application of electro-magnetic ormechanical energy. This yields a wafer 800 having the requiredconductive elements without requiring explicit forming of the openings820.

While the embodiments described above form the openings 820 and locatethe solder elements 822 after the adhesive layer 810 is attach to thewafer 800, another embodiment of the present invention pre-assembles theadhesive layer 810 and solder elements 822. That is, the openings 820are formed and the solder elements 822 are placed in the adhesive layer810 prior to assembly with the wafer 800. For example, in oneembodiment, the adhesive layer 810 is a film-like adhesive layer 810′similar to that shown in FIG. 8C. The openings 820 are formed via lasercutting, chemical etching, die cutting or other methods. The solderelements 822 are then inserted by any of the methods described above. Atthis point, the adhesive layer 810′ with the pre-assembled solderelements 822 is secured to the wafer 800. To minimize deformation priorto applying the adhesive layer 810′, a removable backing (not shown) maybe included with the layer. The removable backing is then removed oncethe layer 810′ is secured.

While not shown in the figures, another embodiment of the presentinvention secures the solder elements 822 to the wafer prior toapplication of the adhesive layer. For example, a PNP is used to place asolder ball 822′ on each connection pad 808. After placing the solderballs 822, the fluid adhesive 810″ is applied. By controlling the volumeof the adhesive applied, the thickness of the adhesive layer 810 iscontrolled relative to the size of the solder balls 822′. Accordingly,the order in which the adhesive layer and solder elements are assembledis not perceived to be critical.

Once the solder elements 822 are positioned and retained within theadhesive layer 810 and the adhesive layer is secured to the wafer 800,the wafer is singulated into individual dice 806 by sawing as shown inFIG. 8H. Once singulated, each individual die 806 with the now integralportion of the adhesive layer 810 and the plurality of solder elements822 forms a pre-packaged flip chip 850 as shown in FIG. 8I in accordancewith the one embodiment. The pre-packaged flip chip 850 is then attachedto a support 102 such as a motherboard (see FIG. 2) where it is, ifnecessary, reflowed to electrically couple and secure it thereto.

Accordingly, various embodiments provide semiconductor device packagesand methods for making semiconductor device packages that areaccomplished at wafer level. While the packaged device and method areuseful for packaging single chips, it is perceived to be particularlyadvantageous for accommodating multiple, stacked devices as furtherdescribed below, allowing even greater chip mounting densities.

One exemplary embodiment of such a pre-packaged multi-flip chip is shownin FIG. 9. Here, a first semiconductor device comprising a die 902 isattached to an active side 903 of a second, larger semiconductor devicecomprising a die 904 over which a flip chip adhesive layer 906 isapplied to produce a pre-packaged, multi-flip chip 900. The multi-flipchip 900, like the flip chip 100 illustrated in FIG. 3, is adapted formounting to a receiving support 950 having an array of conductors 952 asshown in FIG. 10.

The first die 902 (see FIG. 9) includes a first array of connection pads908 while the second die 904 includes a second array of connection pads910 located along the perimeter of the first die 902. The second die 904is sized so that when the first die 902 is secured thereto, the pads 910are still accessible.

FIG. 11 shows an exemplary embodiment of the package 900 in crosssection. The first die 902 is precisely secured to the second die 904with a bonding material 912. The adhesive layer 906 is then placed overthe combined dice 902, 904 according to any of the methods alreadydescribed above. The adhesive layer is sufficiently thick to ensure thatadequate adhesive layer thickness exists over the first die 902. Likethe embodiments described above, the package 900, in one embodiment,includes a protective covering 907 over a back side 905 to protect thepackage 900 during and after processing.

As with the embodiments already described herein, the adhesive layer 906is processed to produce an array of openings 914 which are generallyaligned with the pads 908 and 910. Within each opening 914 is a solderelement 916. The particular shape of the solder elements 916 is variedto accommodate the particular application. For instance, in theembodiment illustrated in FIG. 11, the first array of pads 908 utilizesolder balls 916″ while the second array of pads 910 utilize soldercolumns 916′. In FIG. 12, on the other hand, the first array of pads 908also utilize a solder column 916′. In this particular embodiment, thefirst die 902 has one or more pads 908 connected directly to the seconddie 904 by a wire bond 918 or similar connection. This allowsinterconnection between the circuits on the dice 902, 904 within thepackage 900.

The multi-chip, flip chip package 900 provides increased circuitdensities by stacking multiple dice in a single package. Thus, thepackage occupies less surface area than singularly packaged die andfurther permits electrical interconnection of the dice within thepackage, permitting the use of less complex supports 950 (see FIG. 10);i.e., the support needs no conductive trace to interconnect the variousconductive pads.

Having described a multi-chip flip chip package according to oneembodiment, an exemplary method of making the multi-chip package willnow be described with reference to FIGS. 13A-13K. A first wafer 1300having a first or active side 1302 and a second or backside 1304 isshown in FIG. 13A. A bonding material 1310′ is applied to the back side1304 with a dispensing apparatus 1308 to produce a bonding layer 1310(see FIG. 13B). The bonding layer 1310 may alternatively be applied inthe form of a tape or film (not shown). Once the bonding layer 1310 isformed, the first wafer 1300 is diced as shown in FIG. 13B, producingnumerous first dice 1312 as shown in FIG. 13C. Each die 1312 has anarray of connection pads 1314 which permit electrical connection to thecircuits on the first die 1312.

The first die 1312 is then secured to a second wafer 1316 as shown inFIG. 13D. The second wafer also has a first or active side 1318 and asecond or back side 1320 and numerous, larger second dice 1322 thereon.The bonding layer 1310 permits the back side 1304 of each first die 1312to be secured to the active side 1318 of each second die 1322. In oneembodiment, the bonding layer 1310 is a pressure-sensitive material thatpermits attachment of the dice by application of pressure. In analternative embodiment, the bonding layer is a heat-sensitive material(i.e., thermoplastic or thermoset) that bonds to the second die 1322upon application of heat.

After securing the first die 1312 to the second die 1322, the pads 1314of the first die 1312 are in close proximity and adjacent to pads 1324of the second die 1322. As such, the pads 1314 and 1324 may beinterconnected as shown in FIG. 13E with a wire bond 1326 or similarconnection. After interconnection, an adhesive material 1328′ is appliedto the active side 1318 of the second wafer 1316 with a dispensingapparatus 1329 forming an adhesive layer 1328 as shown in FIG. 13F.

Openings 1330 are then formed within the adhesive layer 1328 as alsoshown in FIG. 13F. As with the embodiments already described herein, theopenings 1330 are substantially aligned with the pads 1324 and 1314 toallow access thereto. The openings may be laser cut, chemically etched,or formed in any one of a variety of ways discussed herein withreference to FIGS. 8A-8I.

Once the openings 1330 are formed, a solder element 1332 is placedtherein as shown in FIG. 13G. In one embodiment, the solder element is aconductive paste material 1332′. In another embodiment, the soldermaterial is a solder ball 1332″. The resulting wafer 1316, as shown inFIG. 13H, has numerous second dice 1322 thereon. Each die 1322 hassolder elements 1332 retained within the adhesive layer 1328 formed onthe active side 1318 of the second wafer 1316 as shown in FIG. 13I. Bythen dicing the second wafer 1316 along the scribe lines as shown inFIG. 13J, numerous individual multi-chip flip chip packages 1350 asshown in FIG. 13K are produced.

Thus, various embodiments can be utilized to package multiple dice atwafer level. By providing multiple dice in one package, higher mountingdensities can be achieved. Furthermore, interconnection between multipledice can be accommodated within the package rather than via thereceiving support.

FIG. 14 illustrates the pre-packaged flip chip 100 according to oneembodiment shown as part of an electronic system 1400 such as acomputer. The system 1400, in one embodiment, includes a processor 1402and an electronic apparatus such as a pre-packaged flip chip 100. Whilediagrammatically depicted as pre-packaged flip chip 100, otherembodiments of the memory component 1404 utilize other flip chips (e.g.,flip chip package 850, 900, or 1350) described herein. In addition, theflip chip package is not limited to use with memory components butrather is adapted for use with most any semiconductor deviceapplication.

Advantageously, the packages and methods of the various embodimentsavoid time-consuming underfill operations by prepackaging a die or diceat wafer level. By packaging the die at wafer level, greatermanufacturing efficiencies are obtainable due to simultaneous processingof multiple dice across the entire wafer face. In addition, the variousembodiments are also particularly amenable to pre-packaging multiplechips in a single module, permitting semiconductor packages havingincreased electronic densities. Since these multi-chip modules can alsobe packaged at wafer level, similar manufacturing economies arerealized.

Preferred embodiments of the present invention are described above.Those skilled in the art will recognize that many embodiments arepossible within the scope of the invention. Variations, modifications,and combinations of the various parts and assemblies can certainly bemade and still fall within the scope of the invention. Thus, theinvention is limited only by the following claims, and equivalentsthereto.

1. A semiconductor wafer, comprising: a plurality of semiconductordevices formed on the wafer, wherein each device includes one or moreconnection pads that are exposed on a first surface of the wafer andelectrically coupled to the semiconductor device; an adhesive layerdisposed on the first surface that includes a plurality of openingsextending through the adhesive layer and aligned with the connectionpads, wherein at least one of the openings includes a chamfered areathat is spaced apart from the connection pads; a conductive materialdisposed in the plurality of openings and operable to provide anelectrical conduction path that extends through the adhesive layer; anda protective coating disposed on an opposing second side of the wafer.2. The semiconductor wafer of claim 1, wherein the wafer comprises atleast one of a silicon-on-sapphire wafer, a silicon-on-insulator waferand a semiconductor wafer that includes one or more epitaxial layers. 3.The semiconductor wafer of claim 1, wherein the conductive materialfurther comprises a solder element.
 4. The semiconductor wafer of claim3, wherein the solder element further comprises a cylindrically-shapedsolder element.
 5. The semiconductor wafer of claim 3, wherein thesolder element further comprises a spherical-shaped solder element. 6.The semiconductor wafer of claim 1, wherein the conductive materialfurther comprises a conductive polymer.
 7. The semiconductor wafer ofclaim 1, wherein the conductive material further comprises a conductivepaste.
 8. The semiconductor wafer of claim 1, wherein the adhesive layerfurther comprises a fluid elastomeric material.
 9. The semiconductorwafer of claim 1, wherein the adhesive layer further comprises a dryadhesive film.
 10. The semiconductor wafer of claim 9, wherein the dryadhesive film further comprises a pressure sensitive film.
 11. Thesemiconductor wafer of claim 1, wherein the adhesive layer is cured byexposing the adhesive layer to at least one of a heat source, a sourceof electromagnetic radiation and a source of ionizing radiation.
 12. Thesemiconductor wafer of claim 1, wherein the conductive material extendsthrough the chamfered area.
 13. The semiconductor wafer of claim 1,wherein the protective coating is an epoxy-based material.
 14. Thesemiconductor wafer of claim 8, wherein the solder element furthercomprises a spherical-shaped solder element.